As fiber networks rapidly expand in terms of scale, passive optical network technologies gradually become a focus of optical access network technologies. A passive optical network includes an optical line terminal (OLT), an optical distribution network (ODN), and an optical network unit (ONU). The ODN includes multiple fiber links, and one or more levels of optical splitters and optical fibers, where an optical splitter is used to split an optical signal or combine optical signals. For example, an optical splitter can split an optical signal sent by an OLT into multiple signals, and transmit the multiple signals to different ONUs through fiber links.
To ensure normal transmission of an optical signal, it is usually required to test quality of an optical fiber and perform fault detection. In the prior art, a test optical signal is usually injected into a passive optical network using an optical time domain reflectometer (OTDR), a reflector is configured at an end (for example, a user end) of a fiber link, the test optical signal is reflected to the OTDR by the reflector, and the OTDR obtains a reflection peak using the received test optical signal, and estimates quality of an optical fiber and locates a fault using a characteristic of the reflection peak.
However, on a passive optical network, an optical splitter is usually configured to split a main fiber link into multiple fiber links, to split one optical signal into multiple branch optical signals, and transmit the multiple branch optical signals to corresponding user ends using the multiple fiber links. In this way, during fiber link maintenance, test signals corresponding to the multiple branch optical signals obtained after splitting are reflected on corresponding fiber links, and after the test signals pass through an optical splitter, the multiple fiber links are overlapped. As a result, the OTDR cannot distinguish and recognize a fiber link corresponding to each branch test optical signal, and consequently cannot determine quality of an optical fiber of a corresponding fiber link according to a reflection peak formed by a test optical signal, and if a fault occurs in a fiber link, the OTDR cannot determine the fiber link in which the fault occurs.